Method and apparatus for determining the contents of a refillable container



Jan; 20, ,1970

METHOD AND APPARATUS FOR DETERMINING THE CONTENTS OF A REFILLABLE CONTAINER Original Filed July 1, 1965 w. E. sooow 3,490,267

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as I E Jan. 20, 1970 w. E. GORDONI 3,490,267

METHOD AND APPARATUS FOR DETERMINING THE CONTENT OF A REFILLABLE CONTAINER Original Filed July 1, 1965 2 Sheets-Sheet 2 P2831025 GAS REFILL TSSTfiR GAS ass-roam FORCE Acrxue on w VALVE PLUNGER 20 2 EXTENT OF VAL E 0PNING+ INVENTOR.

14416707 .5 .Gokoo United States Patent 3,490,267 METHOD AND APPARATUS FOR DETERMINING THE CONTENTS OF A REFILLABLE CONTAINER William E. Gordon, 1351 Terrace Drive, Pittsburgh, Pa. 15228 Original application July 1, 1965, Ser. No. 468 ,tl57, now

Patent No. 3,384,133, dated May 21, 1968. Divided and this application Dec. 21, 1967, Ser. No. 714,381

Int. Cl. G01n 31/00, N22

US. Cl. 7323 2 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus to determine whether the interior of a refillable gas storage cylinder has been contaminated. The outlet passageway of the manually operable control valve has a pressure responsive valve positioned therein. The pressure responsive valve closes the outlet passageway when the gas within the cylinder reaches a predetermined minimum pressure thus retaining a preselected quantity of gas within the cylinder. Since the gas is at a pressure above atmospheric pressure, contaminants cannot enter the cylinder through the valve outlet port. At the refilling station, the pressure responsive valve is manually opened and a sample of the residual gas is withdrawn from the cylinder and analyzed for contaminants. The residual pressure of the gas within the cylinder is also measured to determine whether the pressure responsive valve remained closed to retain the preselected quantity of gas therein. To open the pressure responsive valve, a separate mechanical actuator is inserted in the outlet passageway of the manually operable control valve and urges the pressure responsive valve open against the pressure within the gas cylinder.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a division of application Ser. No. 468,857 filed July 1, 1965, now Patent No. 3,384,133, dated May 21, 1968.

This invention relates to a method and apparatus for determining the contents of a container and more particularly to a method and apparatus for inhibiting corrosion on the interior surfaces of a high pressure gas cylinder and determining the purity of the gas contained therein.

Many gases such as oxygen, nitrogen, hydrogen and helium are commonly dispensed in cylinders initially filled by the vendor to a pressure of about 2,000 psi. The filled cylinders are delivered to the consumer and the consumer attaches a suitable pressure reducing valve in series with the main valve on the cylinder. To use the gas in the cylinder, the customer opens both the main gas valve and the pressure reducer valve and withdraws gas from the cylinder at the desired pressure. When the consumer has exhausted the gas within the cylinder to the extent that the gas pressure has dropped to a level where the consumer can no longer use the gas remaining in the cylinder, the consumer disengages the reducing valve and connects it to another, filled cylinder. The main gas valve on the empty gas cylinder should then be closed and the essentially empty gas cylinder promptly returned to the vendor for refilling. If the consumer adhered to the practice of closing the main gas valve and promptly returning the essentially empty cylinder to the vendor, little, if any, likelihood of contamination would occur.

Unfortunately, the consumers do not all adhere to the recommended practice of closing the main valve on the essentially empty gas cylinder and promptly returning the cylinder to the vendor. Often the main valve is left 3,490,267 Patented Jan. 20, 1970 open, permitting the gas pressure within the cylinder to drop to atmospheric pressure and also permitting air to diffuse through the open valve into the cylinder and contaminate the gas remaining; in the cylinder. Under certam circumstances water may also enter the cylinder through the open main valve and collect on the internal surfaces of the cylinder either by condensing from the atmosphere or by flowing into the cylinder in sizeable quantltles as, for example, when the cylinder is permitted to remain for any appreciable period of time on its side exposed to the elements in a location where water is likely to collect. Some consumers, after a cylinder, especially an oxygen cylinder, has been emptied, use the empty cylinder for their own purposes and, after the empty cylinder has served its special purpose, return the empty cylinder to the vendor in a very dangerous condition. Instances are known where consumers have used an empty oxygen cylinder as a receiver in a compressed air system. Compressed air invariably contains entrained droplets of lubricating oil from the compressor. The internal surface of the gas cylinder when used in this manner becomes coated wtih the lubricating oil. The external surface of the cylinder may not reveal the presence of oil Within the interior portion of the cylinder. The only manner in which the presence of oil Within the cylinder can be detected by the inspection methods now commonly employed is to test for lubricating oil by the odor emanating from the inner portion of the cylinder. There is a substantial probability that lubricating. oil contained within the cylinder will not be detected by its odor.

Because of the manner in which the consumer handles empty gas cylinders, the vendor in refilling the cylinder must exercise great care to make certain that the cylinder' is not contaminated and that it has not been seri ously damaged and weakened by internal corrosion. The problem of contamination is of special concern where it is intended to refill the cylinder with oxygen gas. It is well known that certain combustible liquids such as the hydrocarbons present in lubricating oils may explode when they come in contact with essentially pure oxygen at high pressures. Extremely serious accidents involving multiple deaths and casualties have been attributed to combustible contamination in oxygen cylinders. Responsible vendors, because of this inherent danger, now inspect the cylinders before they are refilled with oxygen. The presently known methods and apparatus for inspecting cylinders have not proven entirely successful and the refilling and use of cylinders filled with high pressure gas remains an inherently dangerous operation.

Briefly, my invention is directed to a method and apparatus for minimizing this inherent danger now present in the refilling and use of cylinders of high pressure gas. I provide a pressure responsive check valve in the outlet opening in the cylinder that limits the amount of gas that can be withdrawn from the cylinder. After the gas within the cylinder has reached a preselected value, the pressure responsive check valve automatically closes the outlet opening and the residual gas remaining within the cylinder can not be exhausted therefrom. The pressure responsive check valve maintains the outlet opening closed and prevents moisture from entering the interior of the cylinder. The vendor upon receiving the exhausted cylinder can quickly and inexpensively determine whether the contents of the cylinder has been contaminated by measuring the pressure of the residual gas remaining in the cylinder and where desired determine the purity of the gas within the cylinder. Where the residual gas pressure is substantially the pressure at which the check valve closes, the vendor may refill the gas cylinder with the same residual gas present in the cylinder. Where the pressure of the residual gas is below the pressure at which the pressure responsive valve is intended to close, the vendor can, by analyzing the residual gas within the cylinder determine whether the pressure responsive valve'is inoperative or whether the cylinder has been contaminated.

Accordingly, the principal object of this invention is to reduce the likelihood of a consumer contaminating a refillable gas cylinder.

Another object of this invention is to provide a simple and inexpensive method for the vendor to determine whether the gas cylinder has been contaminated by the consumer.

These and other objects and advantages of this invention will be more completelydisclosed and described in the following specification, the accompanying drawings and the appended claims.

In the drawings:

FIGURE 1 is a view in section of a gas cylinder having my improved pressure responsive check valve positioned in the outlet of the main valve.

FIGURE 2 is an enlarged view in section of the pressure responsive valve illustrating the manner in which the pressure responsive valve is opened to determine the residual pressure of the gas Within the cylinder and the relative purity thereof.

FIGURE 3 is a diagrammatic view of inspection and refilling stations suitable for use in practicing my invention.

FIGURE 4 is a graphical representation of the pressures required to maintain the valve in an open and closed position.

Although the pressure responsive check valve will be described as associated with the main gas valve, it should be understood that the pressure responsive valve may be positioned elsewere in the gas cyclinder outlet opening and accomplish substantially the same purpose. For proper operation, the diaphragm of the pressure responsive valve should be subjected to the pressure of the gas within the cylinder. Where the pressure responsive valve is positioned in the outlet opening of the main gas valve, the diaphragm is subjected to the pressure of the gas within the cylinder when the main gas valve is opened.

Referring to the drawings and particularly to FIGURE 1 there is illustrated the upper portion of a refillable gas cylinder generally designated by the numeral 10. An externally threaded closure member 12 is positioned within a threaded aperture 14 in the gas cylinder and is secured therein by means of a threaded connection and the annular weld 16. The closure member 12 has an axial threaded bore 18 in which a main gas valve generally designated by the numeral 20 is threadedly secured. A cup shaped cap member 22 is threadedly secured to the closure member 12 to protect the main valve 20 during transportation and the like.

The main gas valve 20 is of conventional construction other than the pressure responsive check valve generally designated by the numeral 24 positioned in the valve outlet 26 and will only be described in sufficient detail to explain its association with the pressure responsive check valve 24. It should be understood that other conventional gas valves may be used in lieu of the main gas valve 20 illustrated in FIGURE 1. The main valve 20 has a body portion 28 with an internal chamber 30. An inlet Passage 32 extends through the body portion 28 into chamber 30 and has an annular valve seat 34. The outlet passage 26 formed in the valve body portion 28 extends into chamber 30 above the valve seat 34. A valve stem 36 is suitably threaded in the valve body portion 28 and has a valve member 38 connected to its lower end portion. A handle 40, upon rotation, moves the valve member 38 toward and away from the annular valve seat 34 to open and close the valve 20. In an open position, that is where the valve member 38 is spaced from the valve seat 34, gas within the cylinder 10 will flow through valve inlet passage 32 into chamber 30 and then through valve outlet passage 26. The valve 20 has a presure relief outlet 42 that is closed by a suitable pressure relief device generally designated by the numeral 44. The pressure relief device 44 is a safety device that is arranged to rupture above a predetermined safe maximum pressure of the gas within the cylinder and relieve the gas pressure on walls of the cylinder 10.

The pressure responsive check valve 24 has a cup shaped body member 46 suitably secured within the valve outlet passageway 26 and has a plurality of passageways 48 therethrough adjacent the peripheral edge portion for the flow of gas from the valve chamber 30 through the valve outlet passageway 26. The cup shaped member 46 has an axial bore 50 therethrough which opens into the cup shaped internal recessed portion 52. A diaphragm 54 has a flexible bottom wall 56 and an annular upturned end wall 58. The diaphragm 54 is positioned within the cup shaped member recessed portion 52 with the diaphragm annular wall 58 fixedly secured to the internal surface of the cup shaped recessed portion 52. The diaphragm bottom wall 56 has a central aperture 60 therein. A conically shaped valve member 62 has a rearwardly extending stem 64 extending in to the diaphragm central aperture 60 and effectively closing the aperture. The conical valve 62 is preferably fabricated of moderately resilient deformable material to permit limited deflection thereon. The front portion of the valve 62 has an annular portion 66 projecting therefrom forming a socket for a fixture, as will be later described.

A tubular member 68 with a central outlet passageway 72 is positioned in the main valve outlet passageway 26 and is suitably secured to the internal cylindrical surface thereof. The tu-bular member 68 has an annular end wall 70 that is adjacent to the cup shaped member 46. A valve seat 74 is formed in the passageway 72 adjacent to the end wall 70 and has an outwardly diverging annular surface. The conical valve member 62 is arranged to seat in the frusto conical valve seat 74 and close the main valve member passageway 26.

Between the diaphragm bottom wall 56 and the internal surface of the cup shaped recess 52 there is a chamber 76. The chamber 76 is filled with a gas at a preselected pressure through the cup shaped member axial passageway 50. A suitable stop member 78 seals the passageway 50 to maintain a preselected gas pressure within the chamber 76. By proper adjustment of the shape of the cup shaped member 46 that supports the diaphragm 54, the depth of the recess 52 in which the diaphragm 54 is positioned and the quantity of the gas introduced into the sealed chamber 76 through passageway 50, the force acting on the valve 62 may be varied as desired. The essential features of the pressure responsive valve are illustrated in FIGURE 4 which is a graph of the force acting on the diaphragm 54 and tending to move it outward to seat valve 62 in valve seat 74 and the annular Opening between the valve 62 and the valve seat 74. In FIGURE 4 the dashed curve X represents the force obtained if the diaphragm were free. Thus with no other forces acting on the diaphragm, the force on the valve is at a minimum and the position of the valve is therefore stable when it is either closed or when it is open at the position corresponding to the point 0 in FIGURE 4. The dash curve Y represents the force on the diaphragm caused by the gas pressure in the sealed chamber 76 when the amount of gas and the shape and size of the chamber are suitably adjusted. The total restoring force is the sum of the free force represented by the curve X and the internal pressure force represented by the curve Y. This summation is illustrated by the solid curve Z in FIG- URE 4. Curve Z, it may be seen, has the desired shape so the valve seat 74. When, however, the external pressure, that is the pressure on the external surface of the diaphragm, is increased by only a relatively small amount above the level corresponding to the level indicated by the letter N so as to create a force represented by the level M, the diaphragm 52 will collapse and the valve 62 will open and remain open as long as the external pressure equals or exceeds the level M. As previously stated, the valve member 62 is preferably formed of a relatively resilient or deformable material and the connection of the valve 62 by stem 64 provides a flexible coupling therebetween so that there is a limited amount of deflection between the diaphragm 54 and the valve 62. This deflection is desirable to provide a positive seal between the valve and valve seat when the valve is moved to a valve closed position.

It should be noted that the pressure responsive check valve generally designated by the numeral 24 requires only a minor modification of the main valve 20. The check valve is preferably mounted on the inside of the valve outlet passageway 26 and the plurality of passages 48 in the cup shaped member 46 allow free passage of the gas from the cylinder through the valve outlet 26 to act on the external surface of the diaphragm 54.

The pressure responsive check valve 24 operates in the following manner and as far as the consumer is concerned the operation of the main valve 20, modified by the installation of the check 24, is essentially the same. When the cylinder is filled with gas at high pressure and the main valve 20 is closed, the check valve 24 will also be closed. When main valve 20 is opened, check valve 24 will open immediately as long as the pressure of the gas within the cylinder exceeds a critical pressure P required to move the diaphragm 54 against the gas pressure within the chamber 76. When the main gas valve 20 is closed, gas will continue to flow out of the main gas valve outlet 26 until the pressure within the outlet 26 drops to the critical pressure P At the critical pressure P the pressure responsive check valve will close. The opening and closing of pressure responsive check valve 24 will not be apparent to the consumer and use of the gas cylinder will be the same as with a conventional main gas valve 20.

When, however, the consumer exhausts the gas within cylinder 10 to an extent that the pressure decreases below the critical pressure P the pressure responsive check valve 24- will close even though main gas valve 20 is open and a residual amount of gas will remain within cylinder 10. This feature is to be distinguished from a gas cylinder having a conventional main valve thereon. The gas in the latter instance continues to exhaust from the cylinder untilthe pressure within the cylinder is substantially equal to atmospheric pressure if the main valve is permitted to remain open.

For example, if the pressure reported by the threshold level N in FIGURE 4, that is the pressure needed to just open the pressure responsive valve 24, is, for illustrative purposes 5% of the initial pressure in the full cylinder, the pressure required to make the pressure responsive check valve 24 move to a fully open position is about only 7% of the initial pressure in the full cylinder. Thus, the consumer will experience no perceptible diminution in the rate of gas delivery from the cylinder until 93% or more of gas is used and exhausted from the cylinder. When 95% of the original gas content has been removed, the pressure responsive check valve 24 will close and the consumer will be unable to exhaust any more gas from the cylinder 10. With the arrangement above described, it is virtually impossible for contamination to enter the cylinder because tliere is a substantial positive gas pressure inside the cylinder even after the consumer has finished using the cylinder. Only if the action of the pressure responsive check valve were mechanically countermanded would it be possible to force a foreign substance into the cylinder. Even when the valve is mechanically countermanded, a substantial pressure would be required to force a contaminant into the cylinder. The force of the contaminant would have to exceed the pressure remaining within the cylinder. It will thus be seen that the pressure responsive check valve prevents the entry of any contaminant into the cylinder.

By retaining a preselected residual gas pressure within the cylinder the vendor can quickly ascertain whether the cylinder has been tampered with, the condition of the pressure responsive check valve and the relative purity of the gas within the cylinder.

The process for testing the cylinder 10 before refilling it with a gas includes two simple and decisive steps. The first step, if positive, will, in a majority of instances, suflice and the second step will not be absolutely necessary. The cylinder as it is returned to the vendor is positioned in the refill line, as diagrammatically illustrated in FIGURE 3. The main gas valve 20 is opened and a conventional pressure tester such as a Bourdon gauge is attached to the main valve outlet 25. The Bourdon gauge has a suitable fixture diagrammatically indicated in FIG- URE 2 by the numeral which is arranged to extend into the central outlet passageway 72 and suitably fits in the annular portion 66 of valve member 62. The fixture 80 is moved in a direction from right to left as viewed in FIGURE 2 to move the valve 62 against the gas pressure in the chamber 76 behind diaphragm 54 and open the pressure responsive check valve 24. The Bourdon gauge will then measure the pressure of the gas within the cylinder 10. If the pressure within the cylinder 10 is essentially the same as the critical pressure P for which the valve is designed, it is almost certain that the internal portion of the cylinder has not be contaminated and the gas remaining in the cylinder is the same gas with which the cylinder was previously filled. If the pressure is significantly below the critical pressure, the vendor may perform a second test to determine whether the pressure responsive check valve 24 is deflective or whether the cylinder and pressure responsive check valve 24 have been tampered with by a consumer.

The second test is to determine the purity of the residual gas within the cylinderg. A sample of the gas is removed from the cylinder and is permitted to flow through a suitable and conventional gas analyzing instrument. In a majority of instances the analytical instrument will be an oxygen analyzer either testing for high purity, in the case of oxygen cylinders, or for oxygen traces, in the case of nitrogen, hydrogen or helium cylinders. If the gas purity is not significantly different from that of the gas with which the cylinder is customarily filled, this second test is a sufficient indication that no impurity has entered the cylinder, even though the check valve has leaked and the pressure within the cylinder is somewhat below the critical pressure P If the gas purity is different from what it should be, the second test is an indication of contamination within the cylinder and the cylinder should be dismantled, inspected and cleaned before refilling. Where the previously described tests indicate that the pressure responsive check valve has functioned properly and the gas content of the cylinder is substantially as pure as when the cylinder was filled on the prior occassion, the vendor may thereafter proceed to fill the cylinder without removing the residual gas remaining therein. In a majority of instances, after making one or both of the previously described brief but positive tests, the vendor will be able to refill the cylinder without first evacuating it to remove the gas remaining inside.

From the foregoing description it will be apparent that by providing a pressure responsive check valve in the gas cylinder 10 that closes at a preselected critical pressure to retain a residual quantity of gas within the cylinder the vendor can now determine, by performing simple inspection tests, whether the cylinder has been contaminated since the cylinder was last refilled.

The inexpensive pressure check valve and the simple inspection tests performed by the vendor now eliminate a substantial number of the hazards encountered in the use of refillable high pressure gas cylinders.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim: 1. A method of supplying gas at an elevated pressure in a refillable gas cylinder and preventing contamination of the gas thereafter introduced into the cylinder during refilling comprising:

filling the cylinder with a gas to a preselected elevated pressure through an outlet passageway of the cylinder, 7

closing a manually operated valve to seal the outlet passageway and maintain the gas within the cylinder at the preselected elevated pressure,

thereafter opening the manually operated valve and withdrawing a substantial portion of the gas from the cylinder, closing a second valve in the cylinder outlet passageway when the pressure of the gas within the cylinder reaches a predetermined minimum pressure to thereby maintain a residual quantity of gas at a pressure above atmospheric pressure within the cylinder,

thereafter measuring the pressure of the residual gas within the cylinder to determine whether the second valve remained closed after the gas within the cylinder reached the predetermined minimum pressure, and

thereafter refilling the cylinder by introducing a sufiicient quantity of additional gas to attain the preselected elevated pressure.

2. A method of supplying gas at an elevated pressure in a refillable gas cylinder and preventing contamination of the gas thereafter introduced into the cylinder durin refilling comprising, 1

filling the cylinder with a gas to a preselected elevate pressure through an outlet passageway of the cylinder, closing a manually operated valve to seal the outlet passageway and maintain gas within the cylinder at the preselected elevated pressure, thereafter opening the manually operated valve an withdrawing a substantial portion of the gas from the cylinder, closing a second valve in the cylinder outlet passageway when the pressure of the gas within the cylinder reaches a predetermined minimum pressure to thereby maintain a residual quantity of gas at a pressure above atmospheric pressure within the cylinder, thereafter opening the second valve and withdrawing a sample of the gas within the cylinder, analyzing the sample of gas to determine whether the gas is the same as the residual gas retained in the cylinder and thereafter filling the cylinder by introducing a sufiicient quantity of additional gas to attain the preselected elevated pressure.

References Cited UNITED STATES PATENTS 2,006,532 7/1935 Bagley 222-66 2,011,393 8/1935 Bradley. 3,266,292 8/ 1966 Bailey 73-23 RICHARD C. QUEISSER, Primary Examiner C. E. SNEE III, Assistant Examiner US. Cl. X.R. 73-4215 

